My 92 Astro ABS brakes begin pressurize and drag by themselves once in a while. They don’t pulse. Turn the car off about5 to 10 secs and they are OK. No one including the dealer can tell me what the problem is.
Does your van also have TCS?
TC and ABS work together and if one acts up the other will too.
Bad wheel sensors or just bad electrical connections can also cause ABS problems.
Perhaps there’s a broken wire to a sensor?